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Summary: Nested Classes | Methods | Inherited Methods

# KeyProtection

`public final class KeyProtection`
`extends Object` `implements KeyStore.ProtectionParameter`

java.lang.Object
↳ | android.security.keystore.KeyProtection

Specification of how a key or key pair is secured when imported into the Android Keystore system. This class specifies authorized uses of the imported key, such as whether user authentication is required for using the key, what operations the key is authorized for (e.g., decryption, but not signing) with what parameters (e.g., only with a particular padding scheme or digest), and the key's validity start and end dates. Key use authorizations expressed in this class apply only to secret keys and private keys -- public keys can be used for any supported operations.

To import a key or key pair into the Android Keystore, create an instance of this class using the `Builder` and pass the instance into `KeyStore.setEntry` with the key or key pair being imported.

To obtain the secret/symmetric or private key from the Android Keystore use `KeyStore.getKey(String, null)` or `KeyStore.getEntry(String, null)`. To obtain the public key from the Android Keystore use `KeyStore.getCertificate(String)` and then `Certificate#getPublicKey()`.

To help obtain algorithm-specific public parameters of key pairs stored in the Android Keystore, its private keys implement `ECKey` or `RSAKey` interfaces whereas its public keys implement `ECPublicKey` or `RSAPublicKey` interfaces.

NOTE: The key material of keys stored in the Android Keystore is not accessible.

Instances of this class are immutable.

### Known issues

A known bug in Android 6.0 (API Level 23) causes user authentication-related authorizations to be enforced even for public keys. To work around this issue extract the public key material to use outside of Android Keystore. For example:

     PublicKey unrestrictedPublicKey =
             KeyFactory.getInstance(publicKey.getAlgorithm()).generatePublic(
                     new X509EncodedKeySpec(publicKey.getEncoded()));

### Example: AES key for encryption/decryption in GCM mode

This example illustrates how to import an AES key into the Android KeyStore under alias `key1` authorized to be used only for encryption/decryption in GCM mode with no padding. The key must export its key material via `Key#getEncoded()` in `RAW` format.

     SecretKey key = ...; // AES key

     KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
     keyStore.load(null);
     keyStore.setEntry(
             "key1",
             new KeyStore.SecretKeyEntry(key),
             new KeyProtection.Builder(KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT)
                     .setBlockMode(KeyProperties.BLOCK_MODE_GCM)
                     .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
                     .build());
     // Key imported, obtain a reference to it.
     SecretKey keyStoreKey = (SecretKey) keyStore.getKey("key1", null);
     // The original key can now be discarded.

     Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
     cipher.init(Cipher.ENCRYPT_MODE, keyStoreKey);
     ...

### Example: HMAC key for generating MACs using SHA-512

This example illustrates how to import an HMAC key into the Android KeyStore under alias `key1` authorized to be used only for generating MACs using SHA-512 digest. The key must export its key material via `Key#getEncoded()` in `RAW` format.

     SecretKey key = ...; // HMAC key of algorithm "HmacSHA512".

     KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
     keyStore.load(null);
     keyStore.setEntry(
             "key1",
             new KeyStore.SecretKeyEntry(key),
             new KeyProtection.Builder(KeyProperties.PURPOSE_SIGN).build());
     // Key imported, obtain a reference to it.
     SecretKey keyStoreKey = (SecretKey) keyStore.getKey("key1", null);
     // The original key can now be discarded.

     Mac mac = Mac.getInstance("HmacSHA512");
     mac.init(keyStoreKey);
     ...

### Example: EC key pair for signing/verification using ECDSA

This example illustrates how to import an EC key pair into the Android KeyStore under alias `key2` with the private key authorized to be used only for signing with SHA-256 or SHA-512 digests. The use of the public key is unrestricted. Both the private and the public key must export their key material via `Key#getEncoded()` in `PKCS#8` and `X.509` format respectively.

     PrivateKey privateKey = ...;   // EC private key
     Certificate[] certChain = ...; // Certificate chain with the first certificate
                                    // containing the corresponding EC public key.

     KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
     keyStore.load(null);
     keyStore.setEntry(
             "key2",
             new KeyStore.PrivateKeyEntry(privateKey, certChain),
             new KeyProtection.Builder(KeyProperties.PURPOSE_SIGN)
                     .setDigests(KeyProperties.DIGEST_SHA256, KeyProperties.DIGEST_SHA512)
                     .build());
     // Key pair imported, obtain a reference to it.
     PrivateKey keyStorePrivateKey = (PrivateKey) keyStore.getKey("key2", null);
     PublicKey publicKey = keyStore.getCertificate("key2").getPublicKey();
     // The original private key can now be discarded.

     Signature signature = Signature.getInstance("SHA256withECDSA");
     signature.initSign(keyStorePrivateKey);
     ...

### Example: RSA key pair for signing/verification using PKCS#1 padding

This example illustrates how to import an RSA key pair into the Android KeyStore under alias `key2` with the private key authorized to be used only for signing using the PKCS#1 signature padding scheme with SHA-256 digest and only if the user has been authenticated within the last ten minutes. The use of the public key is unrestricted (see Known Issues). Both the private and the public key must export their key material via `Key#getEncoded()` in `PKCS#8` and `X.509` format respectively.

     PrivateKey privateKey = ...;   // RSA private key
     Certificate[] certChain = ...; // Certificate chain with the first certificate
                                    // containing the corresponding RSA public key.

     KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
     keyStore.load(null);
     keyStore.setEntry(
             "key2",
             new KeyStore.PrivateKeyEntry(privateKey, certChain),
             new KeyProtection.Builder(KeyProperties.PURPOSE_SIGN)
                     .setDigests(KeyProperties.DIGEST_SHA256)
                     .setSignaturePaddings(KeyProperties.SIGNATURE_PADDING_RSA_PKCS1)
                     // Only permit this key to be used if the user
                     // authenticated within the last ten minutes.
                     .setUserAuthenticationRequired(true)
                     .setUserAuthenticationValidityDurationSeconds(10 * 60)
                     .build());
     // Key pair imported, obtain a reference to it.
     PrivateKey keyStorePrivateKey = (PrivateKey) keyStore.getKey("key2", null);
     PublicKey publicKey = keyStore.getCertificate("key2").getPublicKey();
     // The original private key can now be discarded.

     Signature signature = Signature.getInstance("SHA256withRSA");
     signature.initSign(keyStorePrivateKey);
     ...

### Example: RSA key pair for encryption/decryption using PKCS#1 padding

This example illustrates how to import an RSA key pair into the Android KeyStore under alias `key2` with the private key authorized to be used only for decryption using the PKCS#1 encryption padding scheme. The use of public key is unrestricted, thus permitting encryption using any padding schemes and digests. Both the private and the public key must export their key material via `Key#getEncoded()` in `PKCS#8` and `X.509` format respectively.

     PrivateKey privateKey = ...;   // RSA private key
     Certificate[] certChain = ...; // Certificate chain with the first certificate
                                    // containing the corresponding RSA public key.

     KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
     keyStore.load(null);
     keyStore.setEntry(
             "key2",
             new KeyStore.PrivateKeyEntry(privateKey, certChain),
             new KeyProtection.Builder(KeyProperties.PURPOSE_DECRYPT)
                     .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_RSA_PKCS1)
                     .build());
     // Key pair imported, obtain a reference to it.
     PrivateKey keyStorePrivateKey = (PrivateKey) keyStore.getKey("key2", null);
     PublicKey publicKey = keyStore.getCertificate("key2").getPublicKey();
     // The original private key can now be discarded.

     Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
     cipher.init(Cipher.DECRYPT_MODE, keyStorePrivateKey);
     ...

## Summary

### Nested classes
`class` | `KeyProtection.Builder` Builder of `KeyProtection` instances.

### Public methods
`String[]` | `getBlockModes()` Gets the set of block modes (e.g., `GCM`, `CBC`) with which the key can be used when encrypting/decrypting.
`String[]` | `getDigests()` Gets the set of digest algorithms (e.g., `SHA-256`, `SHA-384`) with which the key can be used.
`String[]` | `getEncryptionPaddings()` Gets the set of padding schemes (e.g., `PKCS7Padding`, `PKCS1Padding`, `NoPadding`) with which the key can be used when encrypting/decrypting.
`Date` | `getKeyValidityForConsumptionEnd()` Gets the time instant after which the key is no long valid for decryption and verification.
`Date` | `getKeyValidityForOriginationEnd()` Gets the time instant after which the key is no long valid for encryption and signing.
`Date` | `getKeyValidityStart()` Gets the time instant before which the key is not yet valid.
`int` | `getPurposes()` Gets the set of purposes (e.g., encrypt, decrypt, sign) for which the key can be used.
`String[]` | `getSignaturePaddings()` Gets the set of padding schemes (e.g., `PSS`, `PKCS#1`) with which the key can be used when signing/verifying.
`int` | `getUserAuthenticationType()`
`int` | `getUserAuthenticationValidityDurationSeconds()` Gets the duration of time (seconds) for which this key is authorized to be used after the user is successfully authenticated.
`boolean` | `isDigestsSpecified()` Returns `true` if the set of digest algorithms with which the key can be used has been specified.
`boolean` | `isInvalidatedByBiometricEnrollment()` Returns `true` if the key is irreversibly invalidated when a new biometric is enrolled or all enrolled biometrics are removed.
`boolean` | `isRandomizedEncryptionRequired()` Returns `true` if encryption using this key must be sufficiently randomized to produce different ciphertexts for the same plaintext every time.
`boolean` | `isUnlockedDeviceRequired()` Returns `true` if the screen must be unlocked for this key to be used for decryption or signing.
`boolean` | `isUserAuthenticationRequired()` Returns `true` if the key is authorized to be used only if the user has been authenticated.
`boolean` | `isUserAuthenticationValidWhileOnBody()` Returns `true` if the key will be de-authorized when the device is removed from the user's body.
`boolean` | `isUserConfirmationRequired()` Returns `true` if the key is authorized to be used only for messages confirmed by the user.
`boolean` | `isUserPresenceRequired()` Returns `true` if the key is authorized to be used only if a test of user presence has been performed between the `Signature.initSign()` and `Signature.sign()` calls.

### Inherited methods
From class `java.lang.Object`
`Object` | `clone()` Creates and returns a copy of this object.
`boolean` | `equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void` | `finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>` | `getClass()` Returns the runtime class of this `Object`.
`int` | `hashCode()` Returns a hash code value for the object.
`final void` | `notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void` | `notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String` | `toString()` Returns a string representation of the object.
`final void` | `wait(long timeout, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void` | `wait(long timeout)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void` | `wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.

## Public methods

### getBlockModes

    public String[] getBlockModes ()

Gets the set of block modes (e.g., `GCM`, `CBC`) with which the key can be used when encrypting/decrypting. Attempts to use the key with any other block modes will be rejected.

See `KeyProperties`.`BLOCK_MODE` constants.

Returns
`String[]` | This value cannot be `null`. Value is `KeyProperties.BLOCK_MODE_ECB`, `KeyProperties.BLOCK_MODE_CBC`, `KeyProperties.BLOCK_MODE_CTR`, or `KeyProperties.BLOCK_MODE_GCM`

### getDigests

    public String[] getDigests ()

Gets the set of digest algorithms (e.g., `SHA-256`, `SHA-384`) with which the key can be used.

See `KeyProperties`.`DIGEST` constants.

Returns
`String[]` | This value cannot be `null`. Value is `KeyProperties.DIGEST_NONE`, `KeyProperties.DIGEST_MD5`, `KeyProperties.DIGEST_SHA1`, `KeyProperties.DIGEST_SHA224`, `KeyProperties.DIGEST_SHA256`, `KeyProperties.DIGEST_SHA384`, or `KeyProperties.DIGEST_SHA512`

Throws
`IllegalStateException` | if this set has not been specified.

See also:

- `isDigestsSpecified()`

### getEncryptionPaddings

    public String[] getEncryptionPaddings ()

Gets the set of padding schemes (e.g., `PKCS7Padding`, `PKCS1Padding`, `NoPadding`) with which the key can be used when encrypting/decrypting. Attempts to use the key with any other padding scheme will be rejected.

See `KeyProperties`.`ENCRYPTION_PADDING` constants.

Returns
`String[]` | This value cannot be `null`. Value is `KeyProperties.ENCRYPTION_PADDING_NONE`, `KeyProperties.ENCRYPTION_PADDING_PKCS7`, `KeyProperties.ENCRYPTION_PADDING_RSA_PKCS1`, or `KeyProperties.ENCRYPTION_PADDING_RSA_OAEP`

### getKeyValidityForConsumptionEnd

    public Date getKeyValidityForConsumptionEnd ()

Gets the time instant after which the key is no long valid for decryption and verification.

Returns
`Date` | instant or `null` if not restricted.

### getKeyValidityForOriginationEnd

    public Date getKeyValidityForOriginationEnd ()

Gets the time instant after which the key is no long valid for encryption and signing.

Returns
`Date` | instant or `null` if not restricted.

### getKeyValidityStart

    public Date getKeyValidityStart ()

Gets the time instant before which the key is not yet valid.

Returns
`Date` | instant or `null` if not restricted.

### getPurposes

    public int getPurposes ()

Gets the set of purposes (e.g., encrypt, decrypt, sign) for which the key can be used. Attempts to use the key for any other purpose will be rejected.

See `KeyProperties`.`PURPOSE` flags.

Returns
`int` | Value is either `0` or a combination of `KeyProperties.PURPOSE_ENCRYPT`, `KeyProperties.PURPOSE_DECRYPT`, `KeyProperties.PURPOSE_SIGN`, `KeyProperties.PURPOSE_VERIFY`, and `KeyProperties.PURPOSE_WRAP_KEY`

### getSignaturePaddings

    public String[] getSignaturePaddings ()

Gets the set of padding schemes (e.g., `PSS`, `PKCS#1`) with which the key can be used when signing/verifying. Attempts to use the key with any other padding scheme will be rejected.

See `KeyProperties`.`SIGNATURE_PADDING` constants.

Returns
`String[]` | This value cannot be `null`. Value is `KeyProperties.SIGNATURE_PADDING_RSA_PKCS1`, or `KeyProperties.SIGNATURE_PADDING_RSA_PSS`

### getUserAuthenticationType

    public int getUserAuthenticationType ()

Returns
`int` | Value is either `0` or a combination of `KeyProperties.AUTH_BIOMETRIC_STRONG`, and `KeyProperties.AUTH_DEVICE_CREDENTIAL`

### getUserAuthenticationValidityDurationSeconds

    public int getUserAuthenticationValidityDurationSeconds ()

Gets the duration of time (seconds) for which this key is authorized to be used after the user is successfully authenticated. This has effect only if user authentication is required (see `isUserAuthenticationRequired()`).

This authorization applies only to secret key and private key operations. Public key operations are not restricted.

Returns
`int` | duration in seconds or `-1` if authentication is required for every use of the key.

See also:

- `isUserAuthenticationRequired()`
- `KeyProtection.Builder.setUserAuthenticationValidityDurationSeconds(int)`

### isDigestsSpecified

    public boolean isDigestsSpecified ()

Returns `true` if the set of digest algorithms with which the key can be used has been specified.

Returns
`boolean` |

See also:

- `getDigests()`

### isInvalidatedByBiometricEnrollment

    public boolean isInvalidatedByBiometricEnrollment ()

Returns `true` if the key is irreversibly invalidated when a new biometric is enrolled or all enrolled biometrics are removed. This has effect only for keys that require biometric user authentication for every use.

Returns
`boolean` |

See also:

- `isUserAuthenticationRequired()`
- `getUserAuthenticationValidityDurationSeconds()`
- `KeyProtection.Builder.setInvalidatedByBiometricEnrollment(boolean)`

### isRandomizedEncryptionRequired

    public boolean isRandomizedEncryptionRequired ()

Returns `true` if encryption using this key must be sufficiently randomized to produce different ciphertexts for the same plaintext every time. The formal cryptographic property being required is indistinguishability under chosen-plaintext attack (`IND-CPA`). This property is important because it mitigates several classes of weaknesses due to which ciphertext may leak information about plaintext. For example, if a given plaintext always produces the same ciphertext, an attacker may see the repeated ciphertexts and be able to deduce something about the plaintext.

Returns
`boolean` |

### isUnlockedDeviceRequired

    public boolean isUnlockedDeviceRequired ()

Returns `true` if the screen must be unlocked for this key to be used for decryption or signing. Encryption and signature verification will still be available when the screen is locked.

Returns
`boolean` |

See also:

- `KeyProtection.Builder.setUnlockedDeviceRequired(boolean)`

### isUserAuthenticationRequired

    public boolean isUserAuthenticationRequired ()

Returns `true` if the key is authorized to be used only if the user has been authenticated.

This authorization applies only to secret key and private key operations. Public key operations are not restricted.

Returns
`boolean` |

See also:

- `getUserAuthenticationValidityDurationSeconds()`
- `KeyProtection.Builder.setUserAuthenticationRequired(boolean)`

### isUserAuthenticationValidWhileOnBody

    public boolean isUserAuthenticationValidWhileOnBody ()

Returns `true` if the key will be de-authorized when the device is removed from the user's body. This option has no effect on keys that don't have an authentication validity duration, and has no effect if the device lacks an on-body sensor.

Authorization applies only to secret key and private key operations. Public key operations are not restricted.

Returns
`boolean` |

See also:

- `isUserAuthenticationRequired()`
- `getUserAuthenticationValidityDurationSeconds()`
- `KeyProtection.Builder.setUserAuthenticationValidWhileOnBody(boolean)`

### isUserConfirmationRequired

    public boolean isUserConfirmationRequired ()

Returns `true` if the key is authorized to be used only for messages confirmed by the user. Confirmation is separate from user authentication (see `isUserAuthenticationRequired()`). Keys can be created that require confirmation but not user authentication, or user authentication but not confirmation, or both. Confirmation verifies that some user with physical possession of the device has approved a displayed message. User authentication verifies that the correct user is present and has authenticated.

This authorization applies only to secret key and private key operations. Public key operations are not restricted.

Returns
`boolean` |

See also:

- `KeyProtection.Builder.setUserConfirmationRequired(boolean)`

### isUserPresenceRequired

    public boolean isUserPresenceRequired ()

Returns `true` if the key is authorized to be used only if a test of user presence has been performed between the `Signature.initSign()` and `Signature.sign()` calls. It requires that the KeyStore implementation have a direct way to validate the user presence for example a KeyStore hardware backed strongbox can use a button press that is observable in hardware. A test for user presence is tangential to authentication. The test can be part of an authentication step as long as this step can be validated by the hardware protecting the key and cannot be spoofed. For example, a physical button press can be used as a test of user presence if the other pins connected to the button are not able to simulate a button press. There must be no way for the primary processor to fake a button press, or that button must not be used as a test of user presence.

Returns
`boolean` |

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